In time division duplex (TDD) RF communications systems, a communications terminal may transmit and receive using a common communications channel. Such transmissions and receptions are not simultaneous and may share a common RF carrier frequency. In some TDD protocols, a transmission may be shortly followed by a reception with a guard period between the transmission and the reception. However, with very short guard periods, the communications terminal may have difficulty transitioning between transmission and reception. FIGS. 1A and 1B illustrate a transmission and reception scenario in which the communications terminal sends a transmit slot 10, which is followed by a guard period 12, which is followed by a receive slot 14 that is received by the communications terminal according to the prior art. An average amplitude 16 of an RF transmit signal sent from the communications terminal has a ramp-up period 18, which is followed by a data burst period 20 that is concurrent with transmission of the transmit slot 10. The data burst period 20 is followed by a ramp-down period 22, which may consume a significant portion of the guard period 12. As such, the communications terminal continues to transmit until completion of the ramp-down period 22. As a result, since the remainder of the guard period 12 may be very short, the communications terminal may have difficulty in preparing to receive the receive slot 14.
In one example, if the communications terminal normally performs a direct current (DC) offset correction of its receiver when transitioning from transmit to receive, the remainder of the guard period 12 may be too short to perform the DC offset correction. Further, if the communications terminal performs the DC offset correction at the beginning of the guard period 12, transmission during the ramp-down period 22 may interfere with the DC offset correction. In another example, when tuning a receive frequency synthesizer in preparation to receive the receive slot 14, the transmission during the ramp-down period 22 may pull a frequency of the receive frequency synthesizer, such that the receiver is not ready to receive the receive slot 14 at the end of the guard period 12. Thus, there is a need to mitigate the effects of transmitting during the guard period 12 in preparation for receiving the receive slot 14.